an arrondissement in the department of the Upper Rhine, in France. The extent is 446 square miles, or 285,440 acres, and it contains seven cantons and 158 communes, with 149,874 inhabitants, in 1851. The chief city of the arrondissement is of the same name, and is situated on a hill whose base is washed by the river Ill, about two leagues from Mulhausen. It has 3371 inhabitants. Long. 7. 11. E. Lat. 47. 37. N.